What does this report contain?
Pages which have a mobile rel alternate link from another page or are AMP pages, but do not correctly canonicalise back; or those which have rel alternate links to a mobile or AMP page that does not reciprocate.
How can this report be used?
To be valid, AMP and mobile alternate pages must canonicalise back to their primary page, and primary desktop pages should have rel=alternate and rel=amphtml. Use this report to find pages which do not have valid alternate tagging.